Methods for independent memory bank maintenance and memory devices and systems employing the same

ABSTRACT

Provided herein are memory devices, systems including memory devices, and methods of operating memory devices in which multiple counters are provided to permit memory refresh commands greater freedom in targeting subsets of the memory device for data refresh operations. In one embodiment, a memory device is provided, comprising a plurality of memory banks, and circuitry configured to (i) store a plurality of values, each of the plurality of values corresponding to one of the plurality of memory banks; (ii) refresh first data stored in a first one of the plurality of memory banks; and (iii) update a first one of the plurality of values corresponding to the first one of the plurality of memory banks based at least in part on refreshing the first data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/930,268, filed May 12, 2020; which is a continuation of U.S. patentapplication Ser. No. 16/734,241, filed Jan. 3, 2020, now U.S. Pat. No.10,692,562; which is a continuation of U.S. patent application Ser. No.16/543,477, filed Aug. 16, 2019, now U.S. Pat. No. 10,541,017; which isa continuation of U.S. patent application Ser. No. 16/375,105, filedApr. 4, 2019, now U.S. Pat. No. 10,482,945; which is a division of U.S.patent application Ser. No. 16/015,441, filed Jun. 22, 2018, now U.S.Pat. No. 10,297,309; which is a continuation of U.S. patent applicationSer. No. 15/870,657, filed Jan. 12, 2018, now U.S. Pat. No. 10,297,307;which claims the benefit of U.S. Provisional Application No. 62/612,004,filed Dec. 29, 2017; each of which is incorporated herein by referencein its entirety.

U.S. patent application Ser. No. 16/543,477, filed Aug. 16, 2019, nowU.S. Pat. No. 10,541,017, is also a continuation of U.S. patentapplication Ser. No. 16/375,073, filed Apr. 4, 2019, now U.S. Pat. No.10,424,365; which is a division of U.S. patent application Ser. No.15/870,657, filed Jan. 12, 2018, now U.S. Pat. No. 10,297,307; whichclaims the benefit of U.S. Provisional Application No. 62/612,004, filedDec. 29, 2017; each of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present disclosure generally relates to semiconductor memorydevices, and more particularly relates to methods for independent memorybank maintenance and memory devices and systems employing the same.

BACKGROUND

Memory devices are widely used to store information related to variouselectronic devices such as computers, wireless communication devices,cameras, digital displays, and the like. Memory devices are frequentlyprovided as internal, semiconductor, integrated circuits and/or externalremovable devices in computers or other electronic devices. There aremany different types of memory, including volatile and non-volatilememory. Volatile memory, including random-access memory (RAM), staticrandom access memory (SRAM), dynamic random access memory (DRAM), andsynchronous dynamic random access memory (SDRAM), among others, mayrequire a source of applied power to maintain its data. Non-volatilememory, by contrast, can retain its stored data even when not externallypowered. Non-volatile memory is available in a wide variety oftechnologies, including flash memory (e.g., NAND and NOR) phase changememory (PCM), ferroelectric random access memory (FeRAM), resistiverandom access memory (RRAM), and magnetic random access memory (MRAM),among others. Improving memory devices, generally, may includeincreasing memory cell density, increasing read/write speeds orotherwise reducing operational latency, increasing reliability,increasing data retention, reducing power consumption, or reducingmanufacturing costs, among other metrics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically illustrating a memory device inaccordance with an embodiment of the present technology.

FIG. 2 is a block diagram schematically illustrating a method for memorybank maintenance in accordance with one aspect of the presentdisclosure.

FIGS. 3A-3D are block diagrams schematically illustrating a method formemory bank maintenance in accordance with one aspect of the presentdisclosure.

FIGS. 4A-4D are block diagrams schematically illustrating a method formemory bank maintenance in accordance with an embodiment of the presenttechnology.

FIG. 5 is a block diagram schematically illustrating a memory system inaccordance with an embodiment of the present technology.

FIG. 6 is a flow chart illustrating a method of operating a memorydevice in accordance with an embodiment of the present technology.

FIG. 7 is a flow chart illustrating a method of operating a memorysystem in accordance with an embodiment of the present technology.

DETAILED DESCRIPTION

The memory cells of a memory device may be periodically refreshed toprevent data loss. For example, volatile memory devices, such as DRAMdevices, may periodically refresh memory cells (e.g., by restoringcharge levels on the memory cells) to prevent data loss due to chargeleakage. Non-volatile memory devices, such as PCM, MRAM, or FeRAMdevices, may periodically refresh memory cells and/or may perform otheroperations to maintain a cell's integrity (e.g., by inverting a datastate therein, overvoltaging, etc.). Maintenance operations are intendedto prevent data loss due to imprint or drift, in which the materialproperties (e.g., polarization) of the cells may be negatively impactedby environmental conditions or the persistent storage of a data statetherein.

One approach to refreshing or maintaining memory cells involvesperforming refresh operations on a per-die basis (e.g., refreshing thesame row of memory cells in every bank of a die simultaneously). Thisapproach can significantly degrade memory device performance as it canprevent an entire die from serving memory requests while beingrefreshed. The per-die approach may also result in a large current drawat the memory device, relative to typical operation, and may thusincrease power consumption by the memory device beyond tolerable limitsfor certain applications (e.g., mobile applications).

Another approach to refreshing or maintaining memory cells involvesperforming operations on a per-bank basis, to permit one memory bank tobe accessed while another bank in the same die is being refreshed ormaintained. In this per-bank approach, the banks can be refreshed in apredetermined order (e.g., round-robin sequentially) or based upon anavailability of the bank to be refreshed (e.g., when the bank is notbeing accessed). Banks could be maintained in a similar manner. If thebanks are refreshed non-sequentially, however, this method may result insome banks going without a refresh or maintenance operation because ofthe memory device's inability to keep and accurately account for whichbanks have been refreshed and which have not.

For instance, memory devices commonly employ a single row counter thatindicates which row is targeted by a refresh operation, and which isincremented once the number of bank-refresh operations is equal to thenumber of banks. This single row counter is relatively simple toimplement and manage, and therefore provides a low-complexity option formanaging refresh operations. But the use of a single row counter mayalso necessitate that before any bank is refreshed a second time, all ofthe banks be refreshed once, lest the row counter increment and cause anun-refreshed row of data in one of the banks to lose data integrity.

To overcome this limitation, several embodiments of the presenttechnology are directed to memory devices, systems including memorydevices, and methods of operating memory devices in which multiplecounters are provided to permit memory refresh commands greater freedomin targeting subsets of the memory device for data refresh operations.In one embodiment, a memory device is provided, comprising a pluralityof memory banks, and circuitry configured to (i) store a plurality ofvalues, each of the plurality of values corresponding to one of theplurality of memory banks; (ii) refresh first data stored in a first oneof the plurality of memory banks; and (iii) update a first one of theplurality of values corresponding to the first one of the plurality ofmemory banks based at least in part on refreshing the first data.

FIG. 1 is a block diagram schematically illustrating a memory device 100in accordance with an embodiment of the present technology. The memorydevice 100 may include an array of memory cells, such as memory array150. The memory array 150 may include a plurality of banks (e.g., banks0-15 in the example of FIG. 1), and each bank may include a plurality ofword lines (WL), a plurality of bit lines (BL), and a plurality ofmemory cells arranged at intersections of the word lines and the bitlines. Memory cells can include any one of a number of different memorymedia types, including capacitive, magnetoresistive, ferroelectric,phase change, or the like. The selection of a word line WL may beperformed by a row decoder 140, and the selection of a bit line BL maybe performed by a column decoder 145. Sense amplifiers (SAMP) may beprovided for corresponding bit lines BL and connected to at least onerespective local I/O line pair (LIOT/B), which may in turn be coupled toat least respective one main I/O line pair (MIOT/B), via transfer gates(TG), which can function as switches. The memory array 150 may alsoinclude plate lines and corresponding circuitry for managing theiroperation.

The memory device 100 may employ a plurality of external terminals thatinclude command and address terminals coupled to a command bus and anaddress bus to receive command signals CMD and address signals ADDR,respectively. The memory device may further include a chip selectterminal to receive a chip select signal CS, clock terminals to receiveclock signals CK and CKF, data clock terminals to receive data clocksignals WCK and WCKF, data terminals DQ, RDQS, DBI, and DMI, powersupply terminals VDD, VSS, VDDQ, and VSSQ.

The command terminals and address terminals may be supplied with anaddress signal and a bank address signal from outside. The addresssignal and the bank address signal supplied to the address terminals canbe transferred, via a command/address input circuit 105, to an addressdecoder 110. The address decoder 110 can receive the address signals andsupply a decoded row address signal (XADD) to the row decoder 140, and adecoded column address signal (YADD) to the column decoder 145. Theaddress decoder 110 can also receive the bank address signal (BADD) andsupply the bank address signal to both the row decoder 140 and thecolumn decoder 145.

The command and address terminals may be supplied with command signalsCMD, address signals ADDR, and chip select signals CS, from a memorycontroller. The command signals may represent various memory commandsfrom the memory controller (e.g., including access commands, which caninclude read commands and write commands). The select signal CS may beused to select the memory device 100 to respond to commands andaddresses provided to the command and address terminals. When an activeCS signal is provided to the memory device 100, the commands andaddresses can be decoded and memory operations can be performed. Thecommand signals CMD may be provided as internal command signals ICMD toa command decoder 115 via the command/address input circuit 105. Thecommand decoder 115 may include circuits to decode the internal commandsignals ICMD to generate various internal signals and commands forperforming memory operations, for example, a row command signal toselect a word line and a column command signal to select a bit line. Theinternal command signals can also include output and input activationcommands, such as clocked command CMDCK. The command decoder 115 mayfurther include one or more registers 117 for tracking various counts orvalues (e.g., counts of refresh commands received by the memory device100 or self-refresh operations performed by the memory device 100).

When a read command is issued and a row address and a column address aretimely supplied with the read command, read data can be read from memorycells in the memory array 150 designated by these row address and columnaddress. The read command may be received by the command decoder 115,which can provide internal commands to input/output circuit 160 so thatread data can be output from the data terminals DQ, RDQS, DBI, and DMIvia read/write amplifiers 155 and the input/output circuit 160 accordingto the RDQS clock signals. The read data may be provided at a timedefined by read latency information RL that can be programmed in thememory device 100, for example, in a mode register (not shown in FIG.1). The read latency information RL can be defined in terms of clockcycles of the CK clock signal. For example, the read latency informationRL can be a number of clock cycles of the CK signal after the readcommand is received by the memory device 100 when the associated readdata is provided.

When a write command is issued and a row address and a column addressare timely supplied with the command, write data can be supplied to thedata terminals DQ, DBI, and DMI according to the WCK and WCKF clocksignals. The write command may be received by the command decoder 115,which can provide internal commands to the input/output circuit 160 sothat the write data can be received by data receivers in theinput/output circuit 160, and supplied via the input/output circuit 160and the read/write amplifiers 155 to the memory array 150. The writedata may be written in the memory cell designated by the row address andthe column address. The write data may be provided to the data terminalsat a time that is defined by write latency WL information. The writelatency WL information can be programmed in the memory device 100, forexample, in the mode register (not shown in FIG. 1). The write latencyWL information can be defined in terms of clock cycles of the CK clocksignal. For example, the write latency information WL can be a number ofclock cycles of the CK signal after the write command is received by thememory device 100 when the associated write data is received.

The power supply terminals may be supplied with power supply potentialsVDD and VSS. These power supply potentials VDD and VSS can be suppliedto an internal voltage generator circuit 170. The internal voltagegenerator circuit 170 can generate various internal potentials VPP, VOD,VARY, VPERI, and the like based on the power supply potentials VDD andVSS. The internal potential VPP can be used in the row decoder 140, theinternal potentials VOD and VARY can be used in the sense amplifiersincluded in the memory array 150, and the internal potential VPERI canbe used in many other circuit blocks.

The power supply terminal may also be supplied with power supplypotential VDDQ. The power supply potential VDDQ can be supplied to theinput/output circuit 160 together with the power supply potential VSS.The power supply potential VDDQ can be the same potential as the powersupply potential VDD in an embodiment of the present technology. Thepower supply potential VDDQ can be a different potential from the powersupply potential VDD in another embodiment of the present technology.However, the dedicated power supply potential VDDQ can be used for theinput/output circuit 160 so that power supply noise generated by theinput/output circuit 160 does not propagate to the other circuit blocks.

The clock terminals and data clock terminals may be supplied withexternal clock signals and complementary external clock signals. Theexternal clock signals CK, CKF, WCK, WCKF can be supplied to a clockinput circuit 120. The CK and CKF signals can be complementary, and theWCK and WCKF signals can also be complementary. Complementary clocksignals can have opposite clock levels and transition between theopposite clock levels at the same time. For example, when a clock signalis at a low clock level a complementary clock signal is at a high level,and when the clock signal is at a high clock level the complementaryclock signal is at a low clock level. Moreover, when the clock signaltransitions from the low clock level to the high clock level thecomplementary clock signal transitions from the high clock level to thelow clock level, and when the clock signal transitions from the highclock level to the low clock level the complementary clock signaltransitions from the low clock level to the high clock level.

Input buffers included in the clock input circuit 120 can receive theexternal clock signals. For example, when enabled by a CKE signal fromthe command decoder 115, an input buffer can receive the CK and CKFsignals and the WCK and WCKF signals. The clock input circuit 120 canreceive the external clock signals to generate internal clock signalsICLK. The internal clock signals ICLK can be supplied to an internalclock circuit 130. The internal clock circuit 130 can provide variousphase and frequency controlled internal clock signal based on thereceived internal clock signals ICLK and a clock enable signal CKE fromthe command/address input circuit 105. For example, the internal clockcircuit 130 can include a clock path (not shown in FIG. 1) that receivesthe internal clock signal ICLK and provides various clock signals to thecommand decoder 115. The internal clock circuit 130 can further provideinput/output (IO) clock signals. The 10 clock signals can be supplied tothe input/output circuit 160 and can be used as a timing signal fordetermining an output timing of read data and the input timing of writedata. The 10 clock signals can be provided at multiple clock frequenciesso that data can be output from and input to the memory device 100 atdifferent data rates. A higher clock frequency may be desirable whenhigh memory speed is desired. A lower clock frequency may be desirablewhen lower power consumption is desired. The internal clock signals ICLKcan also be supplied to a timing generator 135 and thus various internalclock signals can be generated.

The memory device 100 can be connected to any one of a number ofelectronic devices capable of utilizing memory for the temporary orpersistent storage of information, or a component thereof. For example,a host device of memory device 100 may be a computing device such as adesktop or portable computer, a server, a hand-held device (e.g., amobile phone, a tablet, a digital reader, a digital media player), orsome component thereof (e.g., a central processing unit, a co-processor,a dedicated memory controller, etc.). The host device may be anetworking device (e.g., a switch, a router, etc.) or a recorder ofdigital images, audio and/or video, a vehicle, an appliance, a toy, orany one of a number of other products. In one embodiment, the hostdevice may be connected directly to memory device 100, although in otherembodiments, the host device may be indirectly connected to memorydevice (e.g., over a networked connection or through intermediarydevices).

The memory array 150 may be refreshed or maintained as described herein.A refresh operation, as described herein, may be initiated by a hostdevice or memory controller, for example, and may include accessing oneor more rows (e.g., WL) and discharging cells of the accessed row to acorresponding SAMP. While the row is opened (i.e., while the access WLis energized), the SAMP may compare the voltage resulting from thedischarged cell to a reference. The SAMP may then write back a logicvalue (i.e., charge the cell) to a nominal value for the given logicstate. In some cases, this write back process may increase the charge ofthe cell to ameliorate the discharge issues discussed above. In othercases, the write back process may invert the data state of the cell(e.g., from high to low or low to high), to ameliorate hysteresis shift,material depolarization or the like. Other refresh schemes or methodsmay also be employed.

The memory array 150 may be refreshed or maintained using a per-bankscheme in which the same bank of memory array 150 may be refreshedseveral times before another bank of the same rank is refreshed. Thatis, the memory array 150 may be refreshed or maintained withoutrestrictions on the order or frequency for which refresh or othermaintenance operations may be taken on certain banks. Additionally oralternatively, banks of the memory array 150 may be maintained withgreater freedom than legacy per-bank refresh restrictions have imposed.

As set forth above, the memory cells of a memory device may beperiodically refreshed to prevent data loss, either due to chargeleakage or imprint effects. In one approach, illustrated in accordancewith one aspect of the present disclosure in FIG. 2, a memory device 200with multiple memory banks 210-240 may be configured to refresh the samerow 251 of memory cells in every memory bank simultaneously. Memorydevice 200 may be an example of memory device 100 and memory banks210-240 may be examples of banks within memory array 150. In thisapproach, the memory device 200 may be configured to track a single rowaddress (e.g., in a register or counter such as counter 260)corresponding to the most-recently refreshed row (e.g., or thenext-to-be-refreshed row) in each memory bank.

In another approach, in accordance with one aspect of the presentdisclosure in FIGS. 3A-3D, a memory device 300 with multiple memorybanks 310-340 may be configured to refresh the same row 351 of memorycells in every memory bank sequentially. Memory device 300 may be anexample of memory device 100 and memory banks 310-340 may be examples ofbanks within memory array 150. In this regard, FIG. 3A illustrates thememory device 300 after refreshing the row 351 of the first memory bank310, FIG. 3B illustrates the memory device 300 after subsequentlyrefreshing the row 351 of the second memory bank 320, FIG. 3Cillustrates the memory device 300 after refreshing the row 351 of thefourth memory bank 340, and FIG. 3D illustrates the memory device 300after refreshing the row 351 of the third memory bank 330. In thisapproach, the memory device 300 may be configured to track a single rowaddress (e.g., in a register or counter such as counter 360)corresponding to the most-recently refreshed row (e.g., or thenext-to-be-refreshed row) in each memory bank, as well as a count of howmany of the memory banks have been refreshed (e.g., in a register orcounter such as counter 370). When the count of memory banks that havebeen refreshed is increased (e.g., following a refresh operation) toequal the number of memory banks in the memory device 300 (e.g., onceall four banks 310-340 have been refreshed), the tracked row address canbe updated to another row (e.g., a subsequent row or the like) and thecount of the refreshed banks in the counter 370 can be reset to 0.

As previously set forth, a drawback to both of these approaches is thelimitation that a single memory bank, after refreshing a first row,cannot refresh a second row therein until the first row in every othermemory bank is also refreshed (e.g., due to the reliance upon a singletracked row address shared among all the memory banks). Accordingly,embodiments of the present technology may overcome this limitation bytracking addresses for refresh operations on more granular level thanper-bank.

For example, FIGS. 4A-4D are block diagrams schematically illustrating amethod for memory bank maintenance in accordance with an embodiment ofthe present technology. The memory device 400 includes a plurality ofmemory banks 410-440, each having a plurality of rows of memory cells,such as row 451. Memory device 400 may be an example of memory device100 and memory banks 410-440 may be examples of banks within memoryarray 150. The memory device 400 further includes circuitry (e.g., oneor more registers, latches, embedded memories, etc.) such as counters461-464 configured to track row addresses, each corresponding to one ofthe memory banks 410-440. Counters 461-464 may be examples of memoryregisters such as memory register 118 of memory device 100. The memorydevice 400 further includes circuitry (e.g., such as the row decoder140, the column decoder 145, the command decoder 150, the input/outputcircuit 160, WLs, SAMPs, and/or the read/write amplifiers 155 of FIG. 1)configured to refresh data stored in the rows of memory cells of eachbank 410-440. Because separate row addresses are tracked for each bank410-440, the memory device is not constrained to refresh the same row ineach bank 410-440 before refreshing another row in one of the banks 410.

For example, FIG. 4A illustrates the memory device 400 after a first row451 has been refreshed in the first bank 410. Corresponding to thisrefresh operation (e.g., simultaneously with, shortly before or shortlyafter the refresh operation), the value stored in the first row counter461 is updated (e.g., with the address of the updated row 451, oralternatively with an address of a next-to-be updated row). FIG. 4Billustrates the memory device 400 after the first row 451 has beenrefreshed in the second bank 420, subsequent to the refresh of the firstrow 451 in the first bank 410 illustrated in FIG. 4A. Corresponding tothis refresh operation, the value stored in the second row counter 462is updated in a similar fashion.

Turning to FIG. 4C, an advantage of the present approach is readilyapparent, as the memory device 400 is illustrated after a second row 452has been refreshed in the first bank 410, before the first row 451 hasbeen refreshed in the remaining banks 430 and 440 of the memory device.Corresponding to this refresh operation, the value stored in the firstrow counter 461 is again updated (e.g., with the address of the updatedrow 452, or alternatively with an address of a next-to-be updated row).Because memory device 400 tracks separate row addresses for each of thebanks 410-440, the updating of the first row counter 461 poses no threatto the data integrity of the other banks 420-440, unlike the foregoingapproaches illustrated in FIGS. 2 and 3A-3D. As a result of thisadvantage, each bank 410-440 of the memory device 400 can be the targetof a refresh operation (e.g., targeted by a host device connected to thememory device 400) independently of the other banks 410-440 andregardless of the status of the data therein (e.g., regardless ofwhether a refresh operation has recently been performed on the otherbanks, and regardless of the address of most-recently performed refreshoperation thereon). For example, FIG. 4D illustrates the memory device400 after a number of rows 451-455 have been refreshed in the first bank410, only the first row has been refreshed in the second bank 420, aneven greater number of rows has been refreshed in the third bank 430,and no rows have been refreshed in the fourth bank 440.

This approach to memory refresh operations can provide a number ofbenefits relating to efficiency in scheduling refresh operations. Forexample, in a memory device in which one or more banks contain no data,or contain data which is no longer valid, it may provide an increase inperformance to forego performing refresh operations on that memory bank.Moreover, for memory banks of memory media with longer retention times(e.g., with less susceptibility to charge leakage from the chargestorage locations) or less susceptibility to imprint (e.g., with datastorage structures that are more resistant to preferential polarization,domain pinning and/or other undesirable hysteresis shifts whileretaining an unchanging data state), it may be advantageous to scheduleless frequent refresh operations than for memory banks with shorterretention times or greater susceptibility to imprint.

Although in the foregoing example embodiments, memory devices have beendescribed and illustrated as tracking row addresses on a per-bank basisby including a single row counter corresponding to each bank, thoseskilled in the art will readily appreciate that the present technologyhas application to memory devices managing refresh operations withdifferent granularities. For example, memory devices in which the numberof row counters is a multiple of the number of banks, or in which thenumber of banks is a multiple of the number of row counters, can beprovided to track refresh operations on a sub-bank basis (e.g., in whichgroups of rows within a single bank correspond to a row counter), aper-group-of-banks basis, or the like, and can also benefit from theforegoing approach to independent memory maintenance.

Moreover, although in the foregoing example embodiments, memory deviceshave been described and illustrated as performing refresh operations ona per-row basis, those skilled in the art will readily appreciate thatthe present technology has application to memory devices performingrefresh operations on different arrangements of memory cells. Forexample, memory devices in which refresh operations are performed on aper-column basis, a per-block basis, a per-page basis, a per-cell basis,or the like, and can also benefit from the foregoing approach toindependent memory maintenance.

Furthermore, although in the foregoing example embodiments, memorydevices have been described and illustrated as performing refreshoperations (e.g., to restore charge to volatile memory cells or invertdata states in non-volatile memory cells), those skilled in the art willreadily appreciate that the present technology has application to memorydevices utilizing other maintenance operations. In this regard, memorydevices which perform maintenance operations such as backgroundwear-leveling (e.g., in which memory cells which are the target of moreoperations than other memory cells are remapped to more evenlydistribute the wearing effects of operations among memory cells in anarray), garbage collection (e.g., in which memory cells that no longercontain valid data are subjected to delayed processing, such as an eraseoperation or the like) and others can also benefit from the foregoingapproaches to independent memory maintenance.

In accordance with another aspect of the present technology, theadditional freedom of scheduling refresh and other maintenanceoperations provided by the foregoing approach can be utilized to refreshon an “as-needed” basis. In this regard, a memory device or a hostdevice connected thereto can be configured to track operations (e.g.,read operations, write operations, erase operations, activateoperations, etc.) or device uptime and to determine based thereonwhether a refresh operation for a particular row, bank or othersubsection of the memory array is warranted. With the freedom toindependently refresh or maintain banks or other sub-divisions of memoryprovided by the foregoing approach, a memory device can eitherinternally manage its refresh operations (e.g., by determining when arefresh operation is warranted based on tracked activity or uptime andperforming the refresh operation when the refresh target is nototherwise scheduled), or it can facilitate host scheduling of refreshoperations by providing information (e.g., a communication on the memorybus, a voltage on a device pin, etc.) identifying a needed refreshoperation to the host.

In this regard, FIG. 5 is a block diagram of a system 501 having amemory device 500 configured in accordance with an embodiment of thepresent technology. As shown, the memory device 500 includes a mainmemory 502 (e.g., DRAM, NAND flash, NOR flash, FeRAM, PCM, etc.) andcontrol circuitry 506 operably coupled to a host device 508 (e.g., anupstream central processor (CPU)). The main memory 502 includes aplurality of memory units 520, which each include a plurality of memorycells. The memory units 520 can be individual memory dies, memory planesin a single memory die, a stack of memory dies vertically connected withthrough-silicon vias (TSVs), or the like. For example, in oneembodiment, each of the memory units 520 can be formed from asemiconductor die and arranged with other memory unit dies in a singledevice package (not shown). In other embodiments, multiple memory units520 can be co-located on a single die and/or distributed across multipledevice packages. The memory units 520 may, in some embodiments, also besub-divided into memory regions 528 (e.g., banks, ranks, channels,blocks, pages, etc.).

The memory cells can include, for example, floating gate, charge trap,phase change, capacitive, ferroelectric, magnetoresistive, and/or othersuitable storage elements configured to store data persistently orsemi-persistently. The main memory 502 and/or the individual memoryunits 520 can also include other circuit components (not shown), such asmultiplexers, decoders, buffers, read/write drivers, address registers,data out/data in registers, etc., for accessing and/or programming(e.g., writing) the memory cells and other functionality, such as forprocessing information and/or communicating with the control circuitry506 or the host device 508. Although shown in the illustratedembodiments with a certain number of memory cells, rows, columns,regions, and memory units for purposes of illustration, the number ofmemory cells, rows, columns, regions, and memory units can vary, andcan, in other embodiments, be larger or smaller in scale than shown inthe illustrated examples. For example, in some embodiments, the memorydevice 500 can include only one memory unit 520. Alternatively, thememory device 500 can include two, three, four, eight, ten, or more(e.g., 16, 32, 64, or more) memory units 520. Although the memory units520 are shown in FIG. 5 as including four memory regions 528 each, inother embodiments, each memory unit 520 can include one, two, three,eight, or more (e.g., 16, 32, 64, 100, 128, 256 or more) memory regions.

In one embodiment, the control circuitry 506 can be provided on the samedie as the main memory 502 (e.g., including command/address/clock inputcircuitry, decoders, voltage and timing generators, input/outputcircuitry, etc.). In another embodiment, the control circuitry 506 canbe a microcontroller, special purpose logic circuitry (e.g., a fieldprogrammable gate array (FPGA), an application specific integratedcircuit (ASIC), control circuitry on a memory die, etc.), or othersuitable processor. In one embodiment, the control circuitry 506 caninclude a processor configured to execute instructions stored in memoryto perform various processes, logic flows, and routines for controllingoperation of the memory device 500, including managing the main memory502 and handling communications between the memory device 500 and thehost device 508. In some embodiments, the control circuitry can includeembedded memory with memory registers for storing, e.g., row counters,bank counters, memory pointers, fetched data, etc. In another embodimentof the present technology, a memory device may not include controlcircuitry, and may instead rely upon external control (e.g., provided bythe host device 508, or by a processor or controller separate from thememory device).

The host device 508 can be any one of a number of electronic devicescapable of utilizing memory for the temporary or persistent storage ofinformation, or a component thereof. For example, the host device 508may be a computing device such as a desktop or portable computer, aserver, a hand-held device (e.g., a mobile phone, a tablet, a digitalreader, a digital media player), or some component thereof (e.g., acentral processing unit, a co-processor, a dedicated memory controller,etc.). The host device 508 may be a networking device (e.g., a switch, arouter, etc.) or a recorder of digital images, audio and/or video, avehicle, an appliance, a toy, or any one of a number of other products.In one embodiment, the host device 508 may be connected directly tomemory device 500, although in other embodiments, the host device 508may be indirectly connected to memory device (e.g., over a networkedconnection or through intermediary devices).

In operation, the control circuitry 506 can directly write or otherwiseprogram (e.g., erase) the various memory regions of the main memory 502.The control circuitry 506 communicates with the host device 508 over ahost-device bus or interface 510. In some embodiments, the host device508 and the control circuitry 506 can communicate over a dedicatedmemory bus (e.g., a DRAM bus). In other embodiments, the host device 508and the control circuitry 506 can communicate over a serial interface,such as a serial attached SCSI (SAS), a serial AT attachment (SATA)interface, a peripheral component interconnect express (PCIe), or othersuitable interface (e.g., a parallel interface). The host device 508 cansend various requests (in the form of, e.g., a packet or stream ofpackets) to the control circuitry 506. A request can include a commandto read, write, erase, return information, and/or to perform aparticular operation (e.g., a refresh operation, a TRIM operation, aprecharge operation, an activate operation, a wear-leveling operation, agarbage collection operation, etc.).

In some embodiments, the control circuitry 506 can be configured totrack operations (e.g., read operations, write operations, eraseoperations, activate operations, etc.) performed in the main memory 502(e.g., in a register or table in an embedded memory of the controlcircuitry 506) in multiple memory units 520 to facilitate performingrefresh operations on an as-needed basis. In this regard, the controlcircuitry 506 can be configured to compare the number or rate ofoperations experienced by different memory units 520 and to perform orschedule refresh operations on the memory units 520 based at least inpart on a comparison between the number or rate of operationsexperienced by the memory units 520. Alternatively, the controlcircuitry 506 can be configured to perform or schedule refreshoperations on the memory units 520 based at least in part on acomparison of each memory unit 520 to one or more predeterminedthresholds (e.g., threshold numbers of operations, threshold rates ofoperations, etc.). Accordingly, a memory unit 520 which is the target ofoperations that exceed a threshold number or rate can be refreshed morefrequently than another unit 520, due to the freedom with whichdifferent units 520 can be subjected to out-of-order refresh operationsprovided by embodiments of the present technology.

FIG. 6 is a flow chart illustrating a method of operating a memorydevice in accordance with an embodiment of the present technology. Themethod includes storing a plurality of values (box 610), wherein each ofthe plurality of values corresponds to one of a plurality of memorybanks of the memory device. In accordance with one aspect of the presenttechnology, the storing feature of box 610 can be performed by aregister (e.g., register 118 of FIG. 1), an embedded memory, or even amemory array (e.g., memory array 150 of FIG. 1). The method furtherincludes refreshing first data stored in a first one of the plurality ofmemory banks (box 620). In accordance with one aspect of the presenttechnology, the refreshing feature of box 620 can be performed by one ormore of the row decoder 140, the column decoder 145, WL, SAMP, thecommand decoder 150, the input/output circuit 160, the read/writeamplifiers 155, and/or the memory array 150 of FIG. 1. The methodfurther includes updating a first one of the plurality of valuescorresponding to the first one of the plurality of memory banks based atleast in part on refreshing the first data. In accordance with oneaspect of the present technology, the updating feature of box 630 can beperformed by one or more of the command decoder 150 and the register 118of FIG. 1.

The method can further include refreshing, before refreshing data storedin all of the other ones of the plurality of memory banks, second datain the first one of the plurality of memory banks (box 640). Inaccordance with one aspect of the present technology, the refreshingfeature of box 640 can be performed by one or more of the row decoder140, the column decoder 145, WL, SAMP, the command decoder 150, theinput/output circuit 160, the read/write amplifiers 155, and/or thememory array 150 of FIG. 1. The method can further comprise updating thefirst one of the plurality of values based at least in part onrefreshing the second data (box 650). In accordance with one aspect ofthe present technology, the updating feature of box 650 can be performedby one or more of the command decoder 150 and the register 118 of FIG.1.

The method can further include refreshing third data stored in a secondone of the plurality of memory banks (box 660) and updating a second oneof the plurality of values corresponding to the second one of theplurality of memory banks based at least in part on refreshing the thirddata (box 670). In accordance with one aspect of the present technology,the refreshing and updating features of box 660 and 670 can be performedby one or more of the row decoder 140, the column decoder 145, WL, SAMP,the command decoder 150, the register 118 the input/output circuit 160,the read/write amplifiers 155, and/or the memory array 150 of FIG. 1.

FIG. 7 is a flow chart illustrating a method of operating a memorydevice in accordance with an embodiment of the present technology. Themethod includes sending a memory device a first command to refresh firstdata stored in a first one of a plurality of memory banks of the memorydevice (box 710). The method further includes sending the memory device,before sending the memory device one or more commands to refresh datastored in all of the other ones of the plurality of memory banks, asecond command to refresh second data stored in the first one of theplurality of memory banks (box 720). In accordance with one aspect ofthe present technology, the sending features of box 710 and 720 can beperformed by a host device connected to a memory device such as thememory device 100 of FIG. 1.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Furthermore, embodiments from two or more of the methods may becombined.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof. Some drawings may illustrate signals as a single signal;however, it will be understood by a person of ordinary skill in the artthat the signal may represent a bus of signals, where the bus may have avariety of bit widths.

The devices discussed herein, including a memory device, may be formedon a semiconductor substrate or die, such as silicon, germanium,silicon-germanium alloy, gallium arsenide, gallium nitride, etc. In somecases, the substrate is a semiconductor wafer. In other cases, thesubstrate may be a silicon-on-insulator (SOI) substrate, such assilicon-on-glass (SOG) or silicon-on-sapphire (SOP), or epitaxial layersof semiconductor materials on another substrate. The conductivity of thesubstrate, or sub-regions of the substrate, may be controlled throughdoping using various chemical species including, but not limited to,phosphorous, boron, or arsenic. Doping may be performed during theinitial formation or growth of the substrate, by ion-implantation, or byany other doping means.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Otherexamples and implementations are within the scope of the disclosure andappended claims. Features implementing functions may also be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations.

As used herein, including in the claims, “or” as used in a list of items(for example, a list of items prefaced by a phrase such as “at least oneof” or “one or more of”) indicates an inclusive list such that, forexample, a list of at least one of A, B, or C means A or B or C or AB orAC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase“based on” shall not be construed as a reference to a closed set ofconditions. For example, an exemplary step that is described as “basedon condition A” may be based on both a condition A and a condition Bwithout departing from the scope of the present disclosure. In otherwords, as used herein, the phrase “based on” shall be construed in thesame manner as the phrase “based at least in part on.”

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thescope of the invention. Rather, in the foregoing description, numerousspecific details are discussed to provide a thorough and enablingdescription for embodiments of the present technology. One skilled inthe relevant art, however, will recognize that the disclosure can bepracticed without one or more of the specific details. In otherinstances, well-known structures or operations often associated withmemory systems and devices are not shown, or are not described indetail, to avoid obscuring other aspects of the technology. In general,it should be understood that various other devices, systems, and methodsin addition to those specific embodiments disclosed herein may be withinthe scope of the present technology.

What is claimed is:
 1. A memory device comprising: a plurality of memorycells; and circuitry configured to: store a plurality of values, eachvalue of the plurality of values corresponding to a subset of memorycells of the plurality of memory cells, and perform, with a firstfrequency, first maintenance operations on a first subset of memorycells of the plurality of memory cells; update a first value of theplurality of values corresponding to the first subset of memory cellsbased at least in part on performing the first maintenance operations atthe first frequency; perform, with a second frequency different from thefirst frequency, second maintenance operations on a second subset ofmemory cells of the plurality of memory cells; and update a second valueof the plurality of values corresponding to the second subset of memorycells based at least in part on performing the second maintenanceoperations at the second frequency.
 2. The memory device of claim 1,wherein each of the plurality of values corresponds to an address in thecorresponding subset of memory cells.
 3. The memory device of claim 1,wherein the first maintenance operation and the second maintenanceoperation each comprise a refresh operation.
 4. The memory device ofclaim 1, wherein the first maintenance operation and the secondmaintenance operation each comprise one of a refresh operation, a datastate inversion operation, an overvoltaging operation, a wear-levelingoperation, and a garbage collection operation.
 5. The memory device ofclaim 1, wherein the first maintenance operation is of a different kindthan the second maintenance operation.
 6. The memory device of claim 1,wherein the first frequency and the second frequency correspond to aretention time, a susceptibility to imprint, or both, of the firstsubset of memory cells and the second subset of memory cells,respectively.
 7. The memory device of claim 1, wherein the first subsetof memory cells and the second subset of memory cells have differentretention times, different susceptibility to imprint, or both.
 8. Thememory device of claim 1, wherein the plurality of memory cells comprisedynamic random access memory (DRAM) cells, ferroelectric random accessmemory (FeRAM) cells, magnetic random access memory (MRAM) cells, phasechange memory (PCM) cells, or a combination thereof.
 9. The memorydevice of claim 1, wherein the first subset of memory cells and thesecond subset of memory cells comprise different kinds of memory cells.10. The memory device of claim 1, wherein the first subset of memorycells and the second subset of memory cells are comprised by a singleintegrated semiconductor die.
 11. A method comprising: performing afirst maintenance operation on a first subset of a plurality of memorycells of a memory device at a first frequency; and performing a secondmaintenance operation on a second subset of the plurality of memorycells of the memory device at a second frequency different from thefirst frequency.
 12. The method of claim 11, wherein each of the firstmaintenance operation and the second maintenance comprise a refreshoperation.
 13. The method of claim 11, wherein each of the firstmaintenance operation and the second maintenance operation include oneof a refresh operation, a data state inversion operation, anovervoltaging operation, a wear-leveling operation, and a garbagecollection operation.
 14. The method of claim 11, wherein the firstfrequency and the second frequency correspond to a retention time, asusceptibility to imprint, or both, of the first subset and the secondsubset, respectively.
 15. The method of claim 11, wherein the firstsubset of memory cells and the second subset of memory cells havedifferent retention times, different susceptibility to imprint, or both.16. A memory device, comprising: a plurality of memory cells; andcircuitry configured to: perform a first maintenance operation on afirst subset of the plurality of memory cells at a first frequency, andperform a second maintenance operation on a second subset of theplurality of memory cells at a second frequency different from the firstfrequency.
 17. The memory device of claim 16, wherein each of the firstmaintenance operation and the second maintenance comprise a refreshoperation.
 18. The memory device of claim 16, wherein the firstfrequency and the second frequency correspond to a retention time, asusceptibility to imprint, or both, of the first subset and the secondsubset, respectively.
 19. The memory device of claim 16, wherein thefirst subset and the second subset have different retention times,different susceptibility to imprint, or both.
 20. The memory device ofclaim 16, wherein the first subset and the second subset are comprisedby a single integrated semiconductor die.